Barrel for a self-winding timepiece

ABSTRACT

A MAIN SPRING BARREL FOR A TIMEPIECE, PARTICULARLY A SELFWINDING TIMEPIECE, HAS AN INNER CYLINDREICAL WALL TO BE FRICTIONALLY ENGAGED BY THE MAIN SPRING OR A SLIP SPRING ASSOCIATED THEREWITH TO ENABLE SLIPPING OF THE MAIN SPRING RELATIVE TO THE BARREL WHEN THE MAIN SPRING IS SUFFICIENTLY WOUND. THE INNER SURFACE OF THE BARREL HAS A HARDNESS SUBSTANTIALLY EQUAL TO THAT OF THE MAIN SPRING OR THE SLIP SPRING AND HAS SELF-LUBRICATING CHARACTERISTICS. THE INNER BARREL WALL OR SURFACE IS PROVIDED WITH A RELATIVELY WIDE, SHALLOW DEPRESSION THAT EXTENDS OUTWARDLY BEYOND THE CYLINDRICAL SURFACE OF THE INNER WALL, AND CONSTITUTES A DETERRENT TO RELATIVE MOVEMENT BETWEEN THE MAIN SPRING OR ITS SLIP SPRING AND THE INNER BARREL SURFACE BY PROVIDING GRADUALLY SLOPING OR INCLINED AREAS OVER WHICH THE END OF THE SPRING, EITHER MAIN OR SLIP SPRING, MUST PASS.

23, 1971 E. SCHNYDER ETAL 3,621,650

BARREL FOR A SELF-WINDING TIMEPIECE 1 Filed Jan. 22, 1969 INVENTORSEDUARD SCHNYDER CHRISTOPH BIERI ATTORNEYS United States Patent 3,621,650BARREL FOR A SELF-WINDIN G TIMEPIECE Eduard Schnyder and ChristophBieri, Bienne, Switzerland, assignors to Omega Louis Brandt & FrereS.A., Canton, Bern, Switzerland Filed Jan. 22, 1969, Ser. No. 792,963Claims priority, application Switzerland, Jan. 26, 1968, 1,272/68 Int.Cl. G04]; 1/18 US. Cl. 58-87 7 Claims ABSTRACT OF THE DISCLOSURE A mainspring barrel for a timepiece, particularly a selfwinding timepiece, hasan inner cylindrical wall to be frictionally engaged by the main springor a slip spring as sociated therewith to enable slipping of the mainspring relative to the barrel when the main spring is sufficientlywound. The inner surface of the barrel has a hardness substantiallyequal to that of the main spring or the slip spring and hasself-lubricating characteristics. The inner barrel wall or surface isprovided with a relatively wide, shallow depression that extendsoutwardly beyond the cylindrical surface of the inner wall, andconstitutes a deterrent to relative movement between the main spring orits slip spring and the inner barrel surface by providing graduallysloping or inclined areas over which the end of the spring, either mainor slip spring, must pass.

BACKGROUND OF THE INVENTION The main spring or a slip spring associatedtherewith is provided with an outwardly extending tang portion thatfrictionally engages the inner cylindrical surface of the main springbarrel to retard slip between the spring or springs and the barrel. Thisincludes wear, not only of the springs so as to affect the efiiciency ofthe main spring, but also causes malfunction of the timepiece because ofthe main springs gradual change in tension. To offset this situation, itpreviously has been suggested to provide notches in the inner barrelsurface which serve to retard the slipping of the tang on the spring aswell as to provide an audible sound to indicate when the spring hasbecome sufficiently wound.

It has been observed that, in such barrels, the outer coil of the mainspring pressed against the Wall of the barrel attacks this wall, inspite of a good lubrication, thus impairing the operation of thefriction coupling and affecting the working of the timepiece.

SUMMARY OF THE INVENTION According to the present invention, the innerwall of the barrel is generally cylindrical, but has at least onerelatively wide, shallow depression extending outwardly of the innerwall surface to provide gradually sloping or inclined areas adjacent thecylindrical wall areas which serve to gradually inhibit slipping of thetang on the main spring or slip spring but do not induce an abruptstopping or frictional reaction between the spring and the barrel wall.The inner barrel wall constitutes a surface of a hardness substantiallyequal to that of the spring and conveniently may comprise an insert of aharder material than that of which the barrel normally is made.Preferably, the shallow depression is provided in the barrel wall, andthe insert is constituted by a blade spring whose length is equal to thecircumference of the cylindrical portion of the inner wall plus theadditional length produced by the depression, the ends of the bladespring in abutment to place it under compression so that it will followthe contour of the inner wall, including the depression. Preferably, theinsert is self-lubricating and for maximum 3,621,650 Patented Nov. 23,1971 efficiency, there are a plurality of depressions spacedequidistantly around the inner portion of the barrel and whose totalcircumferential area approximately equals that of the cylindricalportions between such depressions.

BRIEF DESCRIPTION OF THE DRAWING The single figure is a top plan view ofa main spring barrel in accordance with the present invention, the mainspring and slip spring being shown to illustrate the environment of theinvention.

The barrel 1 illustrated in the drawing includes a drum 2 adapted tocontain a spiral-coiled main spring m which may be associated with aslip spring S pressing the outer coil of the main spring and itsretarding or brake element B against the inner wall of the drum 3 of thebarrel in order to form a friction coupling preventing overwinding ofthe main spring, the inner end of the spring being secured to the arborA. The inner wall of the barrel presents equidistant shallow depressions4, alternating with cylindrical wall portions 3. In the exampleillustrated, there are six depressions, but this number might bedifferent. Preferably, the depressions 4 have a cylindrical shape andtheir radius of curvature lies between R/ 2 and R, R being the innerradius of the barrel. In a particular embodiment, R is equal to 5.6 mm.and the depth of the depression is less than .1 mm. As seen in thedrawing, the depressions 4 are milled in the mass of the drum 2 of thebarrel.

A blade spring 5, the hardness of which is approximately equal to thatof the main spring, is freely applied against the inner wall of thebarrel drum 2 and takes exactly the shape of the depressions 4 and 0fthe cylindrical wall portions 3. Its length is such that its ends 5abut, so that the blade spring 5 is held in place under compression andcannot rotate with respect to the barrel.

The blade spring 5 is preferably specially manufactured. It is generallysomewhat thinner than the main spring. As concerns its height, it haslittle importance; it is usually scarcely less than the inner height ofthe barrel drum, but is rather larger than the height of the mainspring.

The presence of the depressions 4 ensures, on the one hand, thecompression of the blade spring 5 and, therefore, prevents the latterfrom rotating with respect to the barrel. On the other hand, when theself-winding mechanism tends to wind the main spring, a moment arrivesat which the friction coupling begins to slip; the presence of thedepressions 4 permits controlling this slipping, i.e. the slipping takesplace by small increments, the end of the outer coil of the main springpassing from one depression 4 to the next one; if there were nodepression, a much greater slipping might occur, for instance by onefull turn.

In the example illustrated, the ends 5 of the blade spring 5 abut withinone of the depressions 4, but they might also abut along one of thecylindrical wall portions 3.

The blade spring 5 may be treated so that its surface isself-lubricating, for instance by phosphatization. In a modifiedembodiment, it may be made itself of a selflubricating material.

What we claim is:

1. A main spring barrel for a timepiece, comprising a drum having aninner cylindrical wall against which the outer end of the main spring orslip spring associated therewith frictionally engages to permit relativemovement between the engaging spring and said inner wall to preventover-winding of the main spring, said drum inner cylindrical wall beingcomposed of a hard material and having a self-lubricating surface towithstand frictional wear, said inner cylindrical wall having at leastone relatively wide shallow depression defining an arcuate surfacedisposed outwardly of the cylindrical surface of said inner wall, saiddepression having a circumferential width substantially exceeding itsdepth and including gradually sloping sides to inhibit excessiveslipping of the engaged spring in short and rapid increments relative tosaid inner wall to preclude excessive Wear.

2. A barrel according to claim 1, wherein the depression has acylindrical curvature, the radius of which is between R/ 2 and R, Rbeing the inner radius of the barrel.

3. A barrel according to claim 1, wherein said drum inner wall comprisesan insert defining said cylindrical and depression portions and composedof hard material and providing the frictional surface for engagement bythe respective spring.

4. A barrel according to claim 3, wherein said depression is formed insaid drum and said insert comprises a blade spring having a length equalto the inner circumference of the drum and the depression, the ends ofsaid spring being in abutment and placing the spring under longitudinalcompression to cause it to follow the contour of the depression as wellas the cylindrical surface.

5. A barrel according to claim 1, comprising a plurality of depressionsspaced equally about said drum and having a combined area substantiallyequal to the cylindrical portions between said depressions.

6. A barrel according to claim 5, wherein said depressions are formed insaid drum and said inner wall is lined by an annular spring having alength equal to the inner cylindrical circumference portion of the drumand the depressions, and such as to place said spring under longitudinalcompression to cause it to follow the contour of the depressions as wellas the cylindrical portions.

7. A barrel according to claim 5, wherein the depressions each have acylindrical curvature, the radius of which is between R/2 and R, R beingthe inner radius of the barrel.

References Cited UNITED STATES PATENTS 43,464 7/ 1864 Philippe 58-86410,327 9/1889 Meylan 5886 654,873 7/1900 Church 5887 1,677,045 7/1928Odom 5887 X FOREIGN PATENTS 208,209 1/1940 Switzerland 58-86 RICHARD B.WILKINSON, Primary Examiner G. H. MILLER, ]R., Assistant Examiner

